Siblings of countable cographs
arXiv:2004.12457
Abstract
We show that every countable cograph has either one or infinitely many siblings. This answers, very partially, a conjecture of Thomassé. The main tools are the notion of well quasi ordering and the correspondence between cographs and some labelled ordered trees.
arXiv commentDedicated to the memory of Ivo G. Rosenberg, Three figures, 27 pages
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